Record Breaking Temperature recorded at Cambridge University Botanic Garden: One year On

Just over a year ago, on Thursday 25th July 2019, a temperature reading of 38.7°C was recorded at Cambridge University's Botanic Garden. It was the highest temperature ever officially recorded in the UK, which made international headline news. Sally Petitt, Head of Horticulture, explains how weather is recorded at the Garden and the significance of these exceptional readings.

Activities within the Garden are varied and constantly evolving, but there is one daily task which has been part of our routine for over 100 years, and that is taking meteorological readings.

Today this task is carried out by Katie Martyr, Experimental Section Assistant, who succeeds a long line of dedicated weather observers, including John Kapor (Supervisor, Systematics). The role entails recording a range of readings including maximum and minimum temperatures, ground temperatures, rainfall, cloud cover, and wind speed and direction. Readings are taken at our weather station located in the Experimental Plots, at 9.00am Greenwich Mean Time (so 10.00am in summer), and capture data from the preceding 24 hours.

The station is monitored by the Met Office to ensure that it meets their requirements, and that there have been no changes to the site, such as new buildings or tree growth, which can influence microclimates. The ways of taking readings are relatively low tech, with most observations made using standard thermometers, measuring cylinders and visual observations. The maximum temperature is charted electronically on a thermometer housed in a louvred Stevenson Screen to ensure consistency of measurements. Readings from this thermometer are charted on to a computerised data logger. The reading is then taken by looking for the peak temperature in the preceding 24-hour recording period. All data is logged at the Garden and also with the Met Office which uploads the information on to their publicly accessible Weather Observers Website (WOW). It is this thermometer which took the record 38.7°C reading on 25 July.

In late July, forecasts indicated exceptionally high temperatures. During the week beginning 22 July, the temperature began to rise, and on Thursday 25 July it was evident that the temperature was abnormally high. Plants were wilting and being scorched, glasshouses and ticket offices had to be closed as they were too hot to bear, and staff were flagging - with some resorting to standing in buckets of cold water while potting up plants in the shade!

As usual, the readings for 25 July were not read until 10.00am on 26 July, when Katie excitedly measured a temperature of 38.7°C. This was noted and uploaded onto WOW. It was only later that afternoon the Met Office indicated that this might be a record temperature for the UK. We then waited for the Met Office to check our station before confirming that this was officially a new record. On 29 July they visited the site to calibrate the maximum thermometer computer, and to verify that the weather station and that none of the equipment had been tampered with. It was not until that afternoon that the Met Office declared that we had officially recorded a new maximum temperature for the UK of 38.7°C.

Inevitably this created a great deal of media interest and headlines. From our perspective, the real significance of this chance occurrence was not in reaching this temperature, but in knowing that our continued monitoring of weather here at Cambridge University Botanic Garden was valuable in defining this heatwave.  The University holds readings from our weather station dating back to 1904, though Met Office records show that we have been gathering valuable and continuous data for them since 1891. It is the historical significance of this data which is of real value to the Met Office and climate researchers as they are able to use this to establish how weather patterns are changing over time.

It also acts as a caution about what is happening to our environment, the inevitable consequences for the plants and animals around us, and the impact on our collections. If these new weather patterns become ‘the norm’, then we may need to adapt what we grow in the future. Mediterranean plants do well in our local conditions and there may be scope with changing weather to extend their representation. Conversely, we may also need to review whether we continue to bring in more moisture-loving, temperate species. 

Written by Sally Petitt, Head of Horticulture at CUBG

   

Attention UK Weather Enthusiasts

You may have noticed the two new links that have appeared at the top of the WOW Blog. These may be of particular interest to UK weather observers and enthusiasts, we hope you will find both interesting and useful;-

Daily Weather Summary

As the name suggests 'Daily Weather Summary' holds daily weather summaries from 1860 up to current day. Note these are a monthly publication and are usually available on the website around 6 weeks after the end of every month.

Each summary provides an overview of the weather conditions across the UK for each day based on observations from the network of Met Office synoptic and climate stations, including from our official network of Voluntary Climate sites. Each day includes a table of daily extremes for the UK for key climate variables including temperature, rainfall, sunshine and gust speeds.

 UK Climate Maps and Data

Here you will find a host of fascinating information relating to the UK climate, again all reliant on our network of official observing sites including Voluntary Climate sites, some of which have been recording weather information on behalf of the Met Office for in excess of 100 years. A particular highlight here is the UK Actual and Anomaly Maps section which takes you to a collection of gridded maps derived from Met Office and official Voluntary Climate site data which is interpolated to provide coverage across the UK of up to 1kmx1km resolution. Maps are available for daily, monthly, seasonal and annual timescales, as well as long term averages.

For more information about how the data from our Voluntary Climate Network, usually submitted through WOW, is used please see this blog post.

Guest Blog from a WOW Observer

For as long as I can remember I have had a keen interest in the weather, and, since studying it at university and working for the Met Office for over a decade, meteorology has been huge part of my life. One facet of meteorology I am particularly interested in is statistics: how much rain did we have last month? How many frosts did we have this winter? When did we last have a temperature that high? – the questions are endless. And so when I was gifted a weather station by my wife around 5 years ago now, I saw it as a great opportunity to begin keeping my own records.

My set-up at home is probably quite complex by most people’s standards, but with a bit of time and effort (and money) is relatively straightforward to achieve. I have an Aercus WS3083 which contains a number of instruments connected to a transmitter via RJ11/RJ12 cables, and the wireless transmitter sends the data to a console which resides indoors. 

One issue I have is that my relatively sheltered back garden isn’t really suitably exposed in order to provide gold standard measurements of wind or sunshine, but it is representative of a back garden on the edge of a moderate sized town. So I have made some modifications to it by extending the cables in order to optimally position the various instruments, and the wind/sunshine sensors are currently mounted on a 10ft cranked pole which will eventually be sited on the gable end of my house, at a standard and well exposed 10 metres. I just haven’t found a way of getting it up there yet!

The console indoors is connected to a mini PC, which is always on and permanently connected to the internet. This runs a fantastic piece of software called Cumulus, which interrogates and logs the data from the console at 1-minute intervals. Whilst it does take a little bit of setting up, Cumulus is extremely powerful, and amongst many other things it can upload data to WOW provided you have registered your site and have a WOW account. As a meteorologist by trade, I know the real value that observations and ground truth can have (when viewed with appropriate caution of course!), and the dense network of observations provided by WOW can be really handy when looking at the weather at a local level. So I am happy to think that my observation is contributing to that enhanced data coverage which can be used by local weather enthusiasts and meteorologists alike.

 As well as WOW, Cumulus generates content for a number of webpages I run, including real-time readouts of the 1-minute data, sends me e-mails with daily reports and even generates a text file which can be picked up by an app on my phone so the latest observation is always to hand when I need it. And whilst it’s the statistics that interest me the most, the value to the rest of my family of knowing what the outside temperature is in order to plan what to wear cannot be understated!

Note from the WOW team: We are always interested to add to the list of useful third party software on our support pages. Share your experiences in the comments below to help other users link up with WOW!